The invention relates to a multi-layer, water-soluble or dispersible film having a periodic barrier coating suitable for forming into a container, a method of making such film, a method of packaging a substance in such film, and a container comprising such film. More particularly, the present invention relates to a multi-layer, water-soluble or dispersible film having a continuous water-soluble layer, a barrier coating applied intermittently to discrete areas of the continuous layer, leaving a plurality of uncoated intervals on the continuous layer where the film can be formed into a bag for holding substances that adversely affect the continuous layer of the bag and where the barrier coating is less susceptible or reactive with the substance to be packaged than the continuous layer. The invention also relates, in particular, to a method of making the water-soluble film comprising applying a barrier coating to discrete areas of a continuous water-soluble layer so as to leave a plurality of uncoated intervals on the continuous layer. The invention also relates, in particular, to a method of packaging a substance, where the method comprises forming the aforedescribed multi-layer, water-soluble film into a container, filling the container, and sealing the container, such that the barrier coating forms the inner surface of the container where it prevents the packaged substance from contacting the outer continuous layer, which is more reactive with the packaged substance.
Various types of materials, including non-toxic and potentially hazardous or toxic compounds can be sold in a concentrated form to be dispersed in water or other organic material prior to use. These compounds include, for example, agrichemicals such as herbicides, pesticides, fungicides, insecticides, and fertilizers. Containers are needed for conveniently and safely distributing, selling, and utilizing such materials.
One such container that offers numerous commercial advantages for the packaging of potentially harmful materials is a water-soluble or dispersible containerxe2x80x94e.g., a bag, pouch, package, or related enclosure formed from film. First, via its seal, a water-soluble bag protects the user from accidentally ingesting or otherwise contacting the contents of the package. Second, the precisely measured quantities of the chemical in the bag prevent waste through over charging and minimize accidents. Finally, as the bag dissolves completely in water and the solubilized bag material is biodegradable, there is no potentially hazardous or environmentally destructive packaging material to be discarded.
A variety of cold water-soluble films can be used for the purpose of packaging potentially harmful compounds. A polymeric barrier coating can be affixed to the water-soluble film to minimize or prevent the active material being packaged from chemically or physically interacting with the film surface. When applied onto the water-soluble film, the barrier coating minimizes changes in the properties of the film, protects the activity of the packaged material over the storage life of the package, and provides satisfactory solubility of the film.
One potential problem, however, that could be encountered with multi-layer, water-soluble films is that the presence of continuous coating in the seal-forming area impairs the ability of the film to be heat-sealed. As a result, heat seals formed between two continuous layers of barrier coating are generally weak, peelable, or nonexistent.
Other attempts to address this problem have included the development of a three-layer packaging film comprising a first layer of cold water-soluble film, a second layer of barrier material, and a third layer of cold water-soluble film for forming the heat seal. Use of this film for packaging, however, may present the following concerns: (1) whether the heat-seal layer would insufficiently disperse under various conditions; (2) whether the bond between the third (heat-sealing) layer and the second (barrier) layer would be maintained after sealing; (3) whether a three-layer film is economically feasible; and (4) whether a three-layer film will dissolve in a timely manner.
Consequently, there exists a need for a water-soluble or water-dispersible, multi-layer film that can be used to produce a well-sealed package for materials that adversely affect one or more layers of the film, particularly the layer that forms the outer portion of the package. There also exists a need for a method for making such film and a method of packaging substances in such film.
In accordance with one aspect of the present invention, a multi-layer, cold water-soluble or dispersible film is provided. The multi-layer film comprises: (1) a continuous, cold water-soluble or dispersible material suitable for forming an outer layer of a bag for containing a material therein and having sufficient thickness and strength for use as the bag for containing the material, which may be a solid or a liquid; and (2) a discontinuous barrier coating, suitable for forming an inner layer of a bag, affixed to discrete areas of the continuous layer with areas of the continuous layer being uncoated by the barrier layer. The barrier coating is termed xe2x80x9cdiscontinuousxe2x80x9d because it does not cover at least those areas of the continuous layer that will be formed into a seal or seals when formed into a package or bag. However, the barrier coating is preferably a continuous coating where it is intended to be present since generally its function is to protect the continuous layer from contact with the material contained within the bag or container when the continuous layer forms the outer layer (or at least not the inner layer) of the bag. The discontinuous barrier coating is less reactive than the continuous coating with respect to the substance or material to be packaged, whether a liquid or a solid. Generally, the barrier layer or coating also lacks sufficient structural integrity and strength to contain the contents of the bag once the outer layer is dissolved or dispersed. Thus, the barrier layer is not a structural layer.
In one embodiment, the discontinuity of the barrier coating defines a plurality of uncoated areas, including areas occurring at repeating distances on the continuous layer, which define the seal-forming areas when the film is constructed into a bag. The uncoated area should correspond at least to the areas which will form the bag seal, which may depend on the particular sealing machine that may be utilized. Typically, the outer layer of the bag should have sufficient strength to contain liquids of a specific gravity of about one or more and in a bag volume that contains up to about eight fluid ounces or more, for example, such as up to about two liters.
For example, in accordance with one aspect of the present invention, the uncoated areas may occur along at least one longitudinal end of the continuous layer and at repeating distances spaced apart longitudinally at transverse locations across the continuous layer and are especially useful for a vertical form, fill and seal packaging equipment.
Preferably, the multi-layer, water-soluble film has indicia means for identifying the locations of uncoated areas so as to form the seal-forming areas when the film is used to construct the bag.
The invention is particularly useful for containing materials, whether solid or liquid that attack or degrade or adversely affect the continuous layer.
As used herein, the term xe2x80x9cchemicalxe2x80x9d includes all types of chemicals, including potentially hazardous chemical materials, including organic chemicals such as, but not limited to, agrichemicals, detergents, dyes, pigments, water treatment chemicals and additives, including for concrete, paint and coatings, for example. The term xe2x80x9cagrichemicalsxe2x80x9d includes, for example, agronomically useful chemicals from the following classes: plant nutrients, plant growth regulators, plant protection agents such as pesticides (e.g., herbicides, insecticides, nematocides, fungicides), activity promoters, penetrating agents, synergists, antidotes and safeners, activators, compatibility agents, and adjuvants. The term xe2x80x9cagrichemicalsxe2x80x9d also includes agrichemical compositions (mixtures of one or more agrichemicals with any conventional agronomically acceptable carrier or diluent). The multi-layer film of the present invention can be used to make water-soluble or dispersible packages that are suitable for containing chemicals such as agrichemicals or agrichemical compositions in the form of liquids, solids, or gels. Suitable liquids are, for example, in the form of dispersions, solutions, suspensions, emulsions, and colloids. Solids are in the form of powders, granules, and prills, for example.
The term xe2x80x9ccold waterxe2x80x9d means liquid at a temperature of less than 50xc2x0 C., preferably lower than 35xc2x0 C.; for example, between 5xc2x0 C. and 35xc2x0 C. xe2x80x9cCold water solublexe2x80x9d means completely soluble in cold water. xe2x80x9cDispersiblexe2x80x9d means that the component disintegrates or dissipates into fine particles. For example, particles having a mean particle size of from about 0.1 to about 25 microns, as measured by the CIPAC MT 176 test for dissolution capacity of water soluble-sachets, are considered to be dispersible for the purpose of the present invention. Preferably, for agrichemical use, the dispersed particles are small enough to pass through the orifice of a conventional agrichemical spray apparatus or are filterable without plugging the spray orifice or filter of a conventional agrichemical sprayer.
The term xe2x80x9csubstantially adversely affectxe2x80x9d in the context of contact with the cold water-soluble film by the material desired to be contained, whether an agrichemical material or other chemical material, means that the material is not suitable for containment in a package made of the film because of a deleterious effectxe2x80x94whether a chemical or physical reactionxe2x80x94resulting from contact of the material with the film; including, for example, the material causing the film to dissolve or causing the film components to leach into the material. In addition, the material stored in the package can affect the film, for example, by altering the properties of the film such as by extracting a plasticizer which makes the film brittle or by making the film insoluble or otherwise unsuitable for use in packaging the material.
Typically, the continuous, cold water-soluble layer is much thicker than the barrier coating. Usually, the thickness ratio of the continuous layer to the barrier coating is from about 500:1 to about 2:1, preferably from about 400:1 to about 3:1 and more preferably 60:1 to 5:1. When the multi-layer, cold water-soluble or dispersible film of the invention is used to form a bag and the continuous, water-soluble layer dissolves, the barrier coating releases the chemical in the bag by dissolving or dispersing. Generally, because the barrier coating is thinner than the continuous layer, when the film is formed into a bag, the barrier layer lacks sufficient structural integrity to remain intact after the continuous layer has dissolved or dispersed.
The continuous, cold water-soluble layer can comprise any suitable water soluble material, including but not limited to materials selected from the group consisting of polyvinyl alcohol, polyoxyethylene cellulose derivatives and other materials as hereinafter described, or a combination thereof.
The discontinuous barrier coating can be dispersible or soluble in hot or cold water. To function properly as a xe2x80x9cbarrier,xe2x80x9d this layer should be less susceptible than the continuous layer to interaction with the agrichemical or other material to be packaged.
In accordance with another aspect of the present invention, a water-soluble or dispersible bag is provided for containing various types of materials, the bag being particularly suitable for containing materials, including agrichemicals, that substantially adversely affect cold water-soluble film. The bag is composed of the aforedescribed, inventive film comprising a continuous structural layer of cold water-soluble material and a discontinuous barrier layer affixed to the continuous layer, leaving a plurality of uncoated areas of the continuous layer including at least the areas which will be used to seal the film into a bag or container. For example, for a vertical form, fill and seal device, uncoated areas are located along at least one longitudinal edge of the continuous layer and at repeating distances in transverse locations across the continuous layer or as otherwise required for a specific packaging machine system. The uncoated areas of continuous film form the sealing areas when the film is constructed into the bag. The continuous layer of cold water-soluble film forms the outer layer of the bag, and the barrier layer forms the inner layer of the bag. The continuous layer has sufficient thickness and strength for use as a bag. The barrier coating, which is less susceptible than the continuous layer to interaction with the composition to be packaged, is capable of preventing or mitigating the packaged material from contacting the continuous, cold water-soluble film layer. The barrier coating lacks sufficient structural integrity to contain the chemical in the bag once the water-soluble film layer is substantially dissolved or dispersed. When the bag is placed in water and the water-soluble layer dissolves, the barrier coating dissolves or disperses into particles small enough to disperse or dissolve into the water without clogging the spray system and the material that was contained in the bag is released.
In accordance with one aspect of the invention, the bag is sealed with a material contained therein, which may be a solid or a liquid, for example.
In accordance with still another aspect of the present invention, a method is provided for making a water-soluble film suitable for subsequent construction or fabrication into a bag to contain a chemical that adversely affects the water-soluble film. The method includes intermittently applying a layer of barrier coating onto discrete areas of a continuous layer of water-soluble material, leaving a plurality of uncoated areas on the continuous layer and forming the multi-layer film in accordance with the invention.
In accordance with still another aspect of the present invention, a method is provided for packaging a substance that chemically or physically reacts with a water-soluble film. The method includes forming a water-soluble containerxe2x80x94such as a package, bag, pouch or other containerxe2x80x94from the aforedescribed multi-layer film, by any suitable method and apparatus, where the continuous layer of water-soluble material forms the exterior of the bag and the intermittently applied barrier coating forms the interior of the bag. The method also includes filling the package with a desired amount of the substance to be packaged, and sealing the film together along at least one uncoated interval to form the sealed package so that the inner barrier coating prevents the packaged substance from contacting the outer water-soluble layer.